Mark Zuckerberg

Mark Zuckerberg, born May 14, 1984, was a Harvard undergraduate when he started the Facebook social networking website. An early fan of computers who had developed a "smart" mp3 player in high school, Zuckerberg had previously been reprimanded by the Harvard administration for his Facemash site, a Harvard-specific photo rating site that operated like HotOrNot.com but used photographs taken from Harvard's online facebook, without the subjects' permission. (A facebook, lower-case, is a collection of student photographs designed to introduce students to each other.)

In February of 2004, he started "The Facebook," which took the goals of those lower-case traditional facebooks and combined them with the social networking of Myspace-like sites. Unlike Facemash, The Facebook was opt-in -- any Harvard student could create an account, and by the end of the month, more than half of the undergraduates had done so. Zuckerberg expanded the service quickly, offering it to all Ivy League schools by the end of the spring and more schools the following semester. The Wirehog site was created as a companion filesharing site for Facebook users, and by the end of 2004, The Facebook had over one million registered users.
The advertising revenue made it easier to raise venture capital, and Zuckerberg and his associates purchased the facebook.com domain from its previous holder and dropped the "The" from the site's name. Over time, Facebook became more and more inclusive, opening its doors to all college students, faculty members, and alumni (anyone with a confirmed educational-domain email address), and in 2006 added networks for high school students. Since fall of 2006, the site has been open to anyone who wishes to join -- a shift away from the student-centric origins which many users have decried.
Meanwhile, a Craigslist-like Facebook Marketplace has been added to the site, along with a platform for offering applications. Microsoft purchased a 1.6% stake in the company for $240 million in October of 2007, and the following month the Facebook Beacon service premiered -- a controversial initiative that blends marketing and social networking, which has come under considerable criticism for the way that it can broadcast information about a user's activity outside of the Facebook site, without adequately warning them.